Where You Track Google Algorithm Updates
Google Regularly releases it SEO updates in a Year. From the SEO Point of view you need to track only those Google algorithm updates which affected your top landing pages in Google Search Engine. If your site had penalized or traffic goes down then you can easily track your all events in Google Analytic tool or webmaster tool.
Some of the free tools to analyses Google Algorithm updates are given below :
3. SEO Book
4. Penguin Tool
5. Rank Ranger
6. Search Engine Land
My Favorit Tool are